This invention relates generally to dielectric materials and their use in integrated circuits. More particularly, the invention pertains to novel dielectric polymer compositions, oligomeric precursors and methods for preparing the compositions, and integrated circuit devices fabricated therewith.
Polyimides are known in the art for use in the manufacture of integrated circuits including chips (e.g., chip back end of line, or xe2x80x9cBEOLxe2x80x9d), thin film packages, and printed circuit boards. Polyimides are useful in forming dielectric interlayers, passivation layers, alpha particle barriers, and stress buffers. Polyimides are particularly useful as an interlayer dielectric material to insulate the conductor wiring interconnecting the chips on a multichip module. This is known as xe2x80x9cthin filmxe2x80x9d wiring. Multichip modules represent an intermediate level of packaging between the chips and the circuit board, and are generally known in the art. Multichip modules are made up of multiple layers of power, signal, and ground planes which deliver power to the chips and distribute the input/output signals between chips on the module or to and from the circuit board.
There is a continuing desire in the microelectronics industry to increase the circuit density in multilevel integrated circuit devices, e.g., memory and logic chips, thereby increasing performance and reducing cost. In order to accomplish these goals, those in the field are striving to reduce the minimum feature sizes, e.g., metal lines and vias, and to decrease the dielectric constant of the interposed dielectric material to enable closer spacing of circuit lines without a concomitant increase in crosstalk and capacitive coupling. Polyimides usually have dielectric constants of about 3.0-3.8 and mechanical and thermal properties sufficient to withstand present processing operations including the thermal cycling associated with semiconductor manufacturing. However, there is a need in the art for a dielectric material that would be suitable for use in integrated circuit devices, wherein the material exhibits a lower dielectric constant (e.g.,  less than 3.0) than typically exhibited by polyimides and has improved mechanical and thermal properties.
The invention is addressed to the aforementioned need in the art, and, in one embodiment, provides a novel dielectric composition that represents a significant improvement over prior dielectric materials used in integrated circuit devices. The composition is formed by imidizing and curing an oligomeric precursor compound comprised of a central polyamic acid or polyamic acid ester segment terminated at each end with an aromatic species substituted with two or more aryl-substituted ethynyl moieties. These oligomeric compounds, dielectric compositions formed therefrom, and associated methods of manufacture and use will be discussed in detail herein.
Compounds that are end-capped with two or more diaryl-substituted acetylene moieties at each of two termini are known and described, for example, in PCT Publication No. WO 97/10193. The reference does not, however, describe end-capped oligomeric segments comprised of polyamic acid, a polyamic acid ester, or the like.
U.S. Pat. No. 5,138,028 to Paul et al. is also of interest insofar as polyimides end-capped with diaryl-substituted acetylene are disclosed. Only one diaryl-substituted acetylene moiety is present at each terminus, resulting in higher curing temperature and less efficient cross linking than possible with the oligomeric precursor compounds of the invention.
John et al. (1994), xe2x80x9cSynthesis of Polyphenylenes and Polynaphthalenes by Thermolysis of Enediynes and Dialkynylbenzenes,xe2x80x9d J. Am. Chem. Soc. 116:5011-5012, is of background interest insofar as the publication describes thermal polymerization of substituted enediynes. U.S. Pat. No. 5,773,197 to Carter et al. is also a background reference that is of interest with respect to the present invention, in that the patent describes the manufacture and use of integrated circuit devices in which a dielectric material contained therein is synthesized on a substrate.
No art of which applicants are aware, however, describes or suggests the dielectric compositions as now provided herein, or the oligomeric precursor compounds that are imidized and crosslinked to form the compositions. In contrast to the dielectric materials of the prior art, the present compositions provide the following advantages: (1) the precursor to the present dielectric compositions has a lower solution viscosity than other polyimide precursors, allowing for superior planarization and gap filling; (2) the present dielectric compositions have a low dielectric constant, less than 3.0, which is lower than that of currently used dielectric materials; and (3) films of the novel dielectric compositions have superior mechanical properties relative to current dielectric materials used in the manufacture of integrated circuit devices and packages. The compositions also find utility in laminates, composites and the like.
Accordingly, it is a primary object of the invention to address the above-mentioned need in the art by providing novel dielectric materials that are useful, inter alia, in integrated circuit devices.
It is another object of the invention to provide oligomeric precursor compounds useful for preparing the novel dielectric compositions.
It is still another object of the invention to provide such oligomeric precursor compounds comprised of a central oligomeric segment end-capped at each of two termini with an aryl-substituted acetylene moiety such as an ortho-bis(arylethynyl)aryl group.
It is yet another object of the invention to provide such oligomeric precursor compounds wherein the central oligomeric segment is a polyamic acid, a polyamic acid ester, a polybenzoxazole, or a polybenzothiazole.
It is a further object of the invention to provide methods for synthesizing the oligomeric precursor compounds and methods for preparing the novel dielectric compositions therefrom.
It is still a further object of the invention to provide end-capping reagents comprised of aryl-substituted acetylene compounds, suitable for preparing the aforementioned oligomeric precursor compounds.
It is an additional object of the invention to provide an integrated circuit device in which metallic circuit lines on a substrate are electrically insulated from each other by a dielectric material that comprises a dielectric composition of the invention.
Still a further object of the invention is to provide an integrated circuit packaging device (multichip module) that incorporates a dielectric material comprising a dielectric composition of the invention.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned by practice of the invention.
In a first embodiment of the invention, then, an oligomeric precursor compound is provided that can be imidized and crosslinked to prepare a dielectric material, the oligomeric precursor compound having the structural formula (I) 
wherein:
n is an integer of 2 or more;
q is 0 or 1;
R is an oligomeric unit comprised of polyamic acid, a polyamic acid ester, a polybenzoxazole or a polybenzothiazole;
R1 is an aromatic group optionally substituted at one or more available carbon atoms with an inert, nonhydrogen substituent and optionally containing one or more heteroatoms;
L is a linking group, and, as q may be 0, is optional; and
Ar is arylene optionally substituted at one or more available carbon atoms with an inert, nonhydrogen substituent and optionally containing one or more heteroatoms.
In a related embodiment, the invention pertains to end-capping reagents useful in synthesizing the aforementioned oligomeric precursor compounds, wherein the reagents are comprised of aryl-substituted acetylene compounds generally having the structural formula (II) 
wherein R1, L, q, n and Ar are as defined above, and Z is a reactive moiety such as OH, NH2, COOH, halo, or the like.
In another embodiment of the invention, a novel dielectric composition is provided by heating the aforementioned oligomeric precursor in a manner effective to bring about imidization of the central xe2x80x9cRxe2x80x9d segment of the precursor and crosslinking, or xe2x80x9ccuring,xe2x80x9d at the bis(arylethynyl)aryl-substituted termini. Generally, this involves heating to a predetermined temperature, at a predetermined heating rate, and a predetermined heating time. Preferably, the temperature for preparing the dielectric composition from the oligomeric precursor compound is at least about 250xc2x0 C., more preferably at least about 400xc2x0 C. The dielectric composition so prepared has a dielectric constant of less than about 3.0, a thermal expansion coefficient of less than 10xe2x88x923xc2x0 C.xe2x88x921, and a number of advantages chemical and mechanical properties, e.g., enhanced mechanical and polishing characteristics, enhanced isotropic optical and dielectrical properties, low thermal film stress, resistance to cracking, increased breakdown voltage, optical clarity, good adhesion to a substrate, and the like.
In a further embodiment of the invention, an integrated circuit device is provided that comprises: (a) a substrate; (b) individual metallic circuit lines positioned on the substrate; and (c) a dielectric composition positioned over and/or between the individual metallic circuit lines, the dielectric composition comprising an imidized, cured oligomer precursor compound, the precursor compound having the structural formula (I), i.e., comprising a polyamic acid segment, polyamic acid ester segment, or the like, capped at each terminus with a moiety xe2x80x94Ar(xe2x80x94Cxe2x89xa1Cxe2x80x94(L)qxe2x80x94R1)n wherein Ar, L, q, n, and R1 are as defined above.
Still an additional embodiment of the invention relates to an integrated circuit packaging device providing signal and power current to an integrated circuit chip, the packaging device comprising:
(i) a substrate having electrical conductor means for connection to a circuit board,
(ii) a plurality of alternating electrically insulating and conducting layers positioned on the substrate wherein at least one of the electrically insulating layers is comprised of a dielectric composition comprising an imidized, cured oligomer precursor compound having the structure of formula (I), i.e., comprising a polyamic acid or polyamic acid ester segment capped at each terminus with a moiety xe2x80x94Ar(xe2x80x94Cxe2x89xa1Cxe2x80x94(L)qxe2x80x94R1)n wherein Ar, L, q, n, and R1 are as defined above; and
(iii) a plurality of vias for electrically interconnecting the electrical conductor means, the conducting layers and the integrated circuit chip.